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Age-related changes in total and regional fat distribution

Wednesday, October 07, 2009 Posted by Travis Saunders

As many of our readers know, I performed my MSc under the direction of Dr Bob Ross at Queen's University (Peter is nearing the completion of his PhD in the same lab).  Dr Ross is a world leader in the measurement of body fat and body fat distribution, which is why many of our publications focus on the associations of various body fat depots with markers of metabolic risk.  During my time at Queen's I was also fortunate to work with Drs Jen Kuk and Lance Davidson (now at York and Columbia respectively), who were also studying with Dr Ross.  In the current issue of Ageing Research Reviews, Drs Kuk, Davidson, Ross, and myself review age related changes in body fat distribution in a paper creatively titled "Age-related changes in total and regional fat distribution".

Research from Dr Ross' lab, as well as research done by other groups, has consistently shown that visceral fat is strongly associated with increased metabolic risk.  As part of her PhD thesis, Dr Kuk has even shown that visceral fat is an independent predictor of mortality.  In contrast, after controlling for abdominal fat, the accumulation of lower body subcutaneous fat (the fat just beneath the skin) is often reported to be associated with reduced metabolic risk.  Take for example my MSc thesis which found that after control for abdominal fat, lower body subcutaneous fat is negatively associated with triglyceride levels, and positively associated with HDL cholesterol in elderly men and women.   In other words, if two people have the same amount of abdominal fat, the one with more leg and butt fat is likely to be the healthier of the two.

All of this brings me to our current review, which summarizes the changes in these and other fat depots with normal ageing.  As you might expect, the changes are not good - there is a progressive increase in total abdominal fat (and especially visceral fat), as well as a progressive loss of lower body subcutaneous fat.  So there is more of the bad fat, and less of the good fat.  What's more, these changes can occur even without changes in body weight or waist circumference.  So even without gaining weight, body fat percentage tends to increase with age, and the increase is mostly due to increases in the worst fat depots.  These changes can be seen especially clearly in this image that I created for my thesis introduction (I knew this would come in handy someday!).  Note that although both individuals have a waist circumference of 106cm, the older individual has dramatically more visceral fat, and less thigh subcutaneous fat.



Unfortunately there are other negative changes in body fat distribution with age, including increased fat storage in the heart, liver, bone marrow, and skeletal muscle, all of which are associated with increased metabolic risk, as well as increased risk of fractures in the case of bone marrow.  And as mentioned before, none of these changes are readily apparent when obesity is being measured by BMI or waist circumference alone, which are the most common measures used in the field (and which are pretty accurate in their own right).

But wait - it's not all bad news.  As part of his PhD thesis, Dr Davidson has previously shown that exercise is able to reduce total fat and visceral fat, as well as dramatically improving metabolic risk and functional health in elderly men and women.  So while normal ageing is associated with detrimental changes in body fat distribution, exercise can dramatically reduce these effects.  For what it's worth, Dr Davidson's work has also shown that a combination of aerobic and resistance exercise is the ideal strategy for improving both metabolic and functional health in the elderly.  It doesn't have to be intense (Peter and I helped oversee the resistance exercise in that study, and it was very low intensity for some individuals), but it can have a large impact on your quality of life.  Remember - no matter what your age, it's never too late to improve your health with a little exercise.

Travis

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Kuk, J., Saunders, T., Davidson, L., & Ross, R. (2009). Age-related changes in total and regional fat distribution Ageing Research Reviews, 8 (4), 339-348 DOI: 10.1016/j.arr.2009.06.001

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3 Response to "Age-related changes in total and regional fat distribution"

  1. Anonymous Said,

    How is it possible to tell whether one has more visceral or subcutaneous fat? It would be nice to know what kind I have more of.

    Posted on October 7, 2009 at 8:04 PM

     
  2. Travis Saunders Said,

    That's a great question. Unfortunately, the only ways that I know of for measuring visceral fat involve MRI or CT imaging, both of which are far too costly for the average person. Waist circumference is a good proxy measure, and should be done at the level of the illiac crest (the top of your hip bones). A circumference of >102cm (~40 inches) in men or >88cm in women suggests an excess accumulation of visceral fat.

    As I mentioned in the post, older individuals tend to have more visceral fat for a given waist circumference, but as far as I know there are no specific cut-offs for older individuals. The same is true for Asian individuals, who also have more visceral fat for a given waist circumference.

    As you can see, there is no good answer for how to differentiate between visceral and subcutaneous fat without sophisticated imaging techniques. But since exercise preferentially reduces visceral fat, as well as having other positive health benefits, the best plan is to exercise on a regular basis regardless of your waist circumference or visceral fat levels. And of course, a chat with your physician is always a good way to ascertain your overall health status.

    Travis

    Posted on October 7, 2009 at 9:50 PM

     
  3. Peter Janiszewski, PhD (Cand.), MSc Said,

    Anonymous - a simple rule of thumb:
    If you have a big belly, and it is soft to poke (you can pinch a bunch of fat under the skin) that suggests predominantly subcutaneous fat. On the other hand, if that same big belly is hard - think pregnant woman - that is predominantly due to visceral fat pushing your abdominal musculature outwards.

    But, as Travis already stated - there is no easy way to accurately assess visceral fat, short of getting an MRI or CT scan.

    Posted on October 8, 2009 at 11:08 PM

     

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We are PhD students in the School of Kinesiology and Health Studies at Queen's University in Kingston, Ontario. Our research focuses on the relationships between obesity, physical activity, and health risk. This blog is our attempt to consider the many "cures" for obesity that we read about on a daily basis. Enjoy.

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